Method for the preparation of acrylate dimers and trimers



United States Patent Ofifice 3,342,854 METHOD FOR THE PREPARATION OF ACRYLATE DIMERS AND TRIMERS Joseph W. Nemec, Rydal, and Richard B. Wuchter, Jenkintown, Pa., assignors to Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware N Drawing. Filed Feb. 18, 1965, Ser. No. 433,773 10 Claims. (Cl. 260-485) This invention deals with a method for the preparation of dimers and trimers of acrylates having the formula CH =CHCOOR where R has the significance given heretofore.

R may typically represent methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, tetradecyl and octadecyl, in any of the known spatial structures, such as normal, iso and tertiary. Typical acrylate reactants include methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, t-dodecyl acrylate and octadecyl acrylate.

The process of the present invention employs a catalyst defined by the formulas:

and ROOCGCHzCHOHzOHzCOOR In compounds (I) and (II), R" and R' may be the same or different, as desired. In compound (II), the R groups may be the same or different, as desired.

R represents alkyl groups of 1 to 18 carbon atoms, preferably 1 to 4 carbon atoms, phenyl, or alkyl-substituted phenyl in which the alkyl substituent may be represented by one or more alkyl groups in which the total carbon content of the alkyl substitution ranges from 1 to 8 carbon atoms.

R" and R' represent alkyl of 1 to 18 carbon atoms, preferably 1 to 4 carbon atoms. Furthermore, the R" and R' groups, collectively with the nitrogen atom to which they are attached, may form a saturated cyclic'amine group containing up to 5 carbon atoms in the ring and optionally containing one or more alkyl substituents having a total of up to 6 carbon atoms. This cyclic amine group may also contain an oxygen atom or a sulfur atom in the ring, if desired.

The R" and R' group s as alkyl embodiments may possess inert substituents as long as the carbon atom attached to the nitrogen is primary in structure. Such inert substituents include cyano, chloro, bromo, alkoxy or carbalkoxy moieties, among others. These are within the gamut of this invention.

Patented Sept. 19, 1967 formula:

typically include N,N,N,N tetramethyl-P-phenylphosphonous diamide, N,N,N,N-tetra-n-butyl-P-phenylphosphonous diamide, N,N-dimethyl-N',N'-dioctyl-P-pheny1 phosphonous diamide, N,N,N',N' tetra-n-butyl-P-ethylphenylphosphonous diamide, N,N,N',N' tetramethyl-P- tolylphosphonous diamide, N,N,-diethyl-N,N'-di-n-butyl- P octylphenylphosphonous diamide, phenyldipiperidyl phosphine and tolyldimorpholino phosphine.

Specific embodiments of the catalyst having the formula:

may be methyl,

R'" (1 include N,N dirnethyl-P,P-diphenylphosphinous amide, N,N diethyl P,P diethylphosphinous amide, N,N-di-nbutyl-P,P-diphenylphosphinous amide, N,N -dioctyl-P,P- diphenylphosphinous amide, N-methyl-N-dodecyl-P,P-diphenylphosphinous amide, N,N-dimethyl-P,P-ditolylphos phinous amide, N,N dibutyl P,P dioctylphenylphosphinous amide, piperazinodiphenyl phosphine and pyrrolidinylditolyl phosphine.

The specific catalyst (I), as defined above, is employed in the present preparation of dimers and trimers in amounts as low as about 0.25 mole percent, but is preferably used in the range of about 0.7 to 1.5 mole percent, With respect to the acrylate reactant. Greater amounts can be employed, if desired, but generally there is no advantage. The specific catalyst (11), as defined above, is used in amounts of up to about 8 mole percent, preferably 3 to 5 mole percent, with respect to the acrylate reactant. Actually, the upper amount of catalyst used is dictated largely by the economics of the process.

The catalyst may be employed as such or prepared in situ, as desired. If preparation in situ is contemplated, one employs the R'-dichlorophosphine or (R') -chlorophosphine, as the case may be, and the appropriate amines, as will be understood by those skilled in the art. If the phosphonous diamide is to be used, then 4 moles of the amine is employed per mole of the R-clichlorophosphine. If the phosphinous amide is to be used, there is employed 2 moles of the amine per mole of the (R') -chlorophosphine. In either instance, the in situ preparation involves the formation of an amine salt which must be substantially completely removed, such as by filtration or Washing, as desired.

The present process is conducted in the range of about 0 to 100 0, preferably 25 to C. The pressure is not critical and the reaction is generally performed at atmospheric pressure, although subatmospheric and superatmospheric pressures are suitable. If desired, nitrogen or other inert atmosphere may be used and in some instances is preferable, particularly when the amides employed are derived from low molecular weight amine, such as dimethylamine.

A solvent is not required in the present process, although it is frequently desirable to employ an inert,

volatile, organic solvent. Typically, one may use acetonitrile, hexane, benzene, toluene or the like.

One may conduct the reaction by adding the acrylate to the catalyst or the reverse, as desired. It is preferred to add the acrylate incrementally to the catalyst, with or without a solvent, at a rate substantially consistent with the rate of reaction. The reaction is somewhat exothermic in nature and the incremental addition of the acrylate to the catalyst can be regulated to moderate the heat of the exothermic reaction.

Small amounts of Water can be tolerated in the reaction mixture without any noticeable deterrence. However, larger amounts of water, such as 5 to by weight, based on the acrylate, is enough to inhibit considerably the desired process. This should be kept in mind if the amine salt formed from the in situ preparation of the catalyst is washed out of the reaction mixture.

At the conclusion of the reaction, the desired product is separated by distillation techniques. Unreacted material, if any, and solvent, if one is employed, are removed first and then the dimer is next isolated, followed finally by the trimer. Usually, the dimer is formed in greater amounts than the trimer and typically the product will be 60 to 85% or more dimer and 8 to 10% trimer. They are readily separated by distillation as mentioned hereinbefore.

The dimer and trimer products are useful monomers and chemical intermediates. The trimer is particularly useful in the production of copolymers, especially with methyl methacrylate and styrene, as well as other comonomers, where the trimer also provides valuable plasticizing properties to the copolymers. Because of the unique structure of the trimer, said trimer may be used to provide cross-linking to such a polymer system to form useful resins for protective coatings for wood, metal and the like. Typically, in this respect, a useful copolymer consists of 40% methyl methacrylate, 40% styrene and 20% of the trimer of this invention, all parts being by weight. These copolymers are effective coatings that are resistant to cracking and have good impact strength. Especially valuable are those copolymers made from the trimer of this invention wherein the symbol R represents ethyl.

By adhering strictly to the aforementioned conditions, one is able to produce consistently and economically high yields of desired product without any appreciable, undesirable side effects.

The present process may be more fully understood from the following examples which are offered by way of illustration and not by way of limitation.

Example 1 Ethyl acrylate (400 g.) inhibited with monocthylether of hydroquinone was added slowly (one hour) to a stirred solution at 75 C. containing 11.0 g. of phenyldipiperidyl phosphine dissolved in 100 ml. of toluene. The entire operation was performed under nitrogen. The reaction mixture was held at 75 C. for an additional hour and then distilled. There was recovered 87 g. of ethyl acrylate before 267 g. of diethyl 2-methyleneglutarate was obtained on vacuum distillation. The dimer distilled at 68 C. at 0.3 mm. and had n =l.4377. The residue contained 35 g. of diethyl 2-methylene-4-carbethoxypimelate, B.P. 100 C. at 0.1 mm., n =1.4470.

Example 2 Dichlorophenyl phosphine (7.1 g.) was added slowly to a stirred solution maintained at 0 C. and containing 11.7 g. of anhydrous diethylamine dissolved in 50 ml. of benzene. The reaction mixture was permitted to stir two hours at 25 C. after the addition. The reaction mixture was then treated with 50 m1. of water, the layers were separated and the organic layer was further washed with 50 ml. of water. Ethyl acrylate (400 g.) containing monomethylether of hydroquinone was then added over one hour to the stirred washed benzene solution maintained at 65 C. After allowing the reaction to proceed one hour after the addition, the reaction mixture was distilled. There was obtained 328 g. of diethyl Z-methyleneglutarate and 44 g. of diethyl 2-methylene-4-carbethoxypimelate.

Example 3 Dichlorophenyl phosphine (7.1 g.) was added slowly to a stirred solution under nitrogen at 0 C. and containing 8.6 g. of anhydrous dimethylamine dissolved in 75 ml. of hexane. After stirring an additional two hours at room temperature, the mixture was filtered with suction. The solid was washed with an additional 25 ml. of hexane. The hexane-catalyst solution was used directly. Ethyl acrylate (400 g.) inhibited with monomethylether of hydroquinone was added over one hour to the catalyst solution maintained at 65 C. and under an atmosphere of nitrogen. The reaction mixture was permitted to stir an additional two hours at 65 C. after the addition. Ethyl acrylate (226 g.) was recovered by distillation. Vacuum distillation of the residue produced 104 g. of diethyl 2-methyleneglutarate and 30 g. of diethyl 2- methylene-4-carbethoxypimelate.

In a similar way, there is employed as catalyst N,N,N',N-tetramethyl-P-butylphosphonous diamide.

Example 4 Chlorodiphenyl phosphine (22.0 g.) was added slowly to a stirred solution containing 25.8 g. of di-n-butylamine dissolved in ml. of hexane. The reaction mixture was maintained at 0 to 10 C. during the addition and then permitted to stir an additional two hours at room temperature. The reaction mixture was filtered with suction and the amine salt was washed with 25 ml. of hexane. Ethyl acrylate (333 g.) containing monomethylether of hydroquinone was added slowly (one hour) to the hexane solution of the catalyst maintained at 60 to 65 C. After permitting the reaction to proceed four hours at 65 C. after the addition, 296 g. of ethyl acrylate was recovered on distillation. Diethyl Z-methyleneglutarate (29.5 g.) and diethyl Z-methylene-4-carbethoxypimelate (3.2 g.) were obtained on vacuum distillation.

Example 5 Chlorodiphenyl phosphine (22.0 g.) dissolved of benzene was added slowly to a solution at 0 to 10 C. containing 15.4 g. of diethylamine dissolved in 50 ml. of benzene. After the addition, the mixture was heated to reflux under nitrogen for two hours. After cooling the reaction mixture to room temperature, the salt was extracted with 75 ml. of water. The organic layer was again washed with 50 ml. of water. Ethyl acrylate (200 g.) inhibited with monomethylether of hydroquinone was then added dropwise to the benzene solution of the catalyst maintained at 65 C. After a reaction period of two hours at 65 C., the reaction solution was distilled yielding 172 g. of ethyl acrylate. On vacuum distillation, 21.5 g. of diethyl 2-methyleneglutarate and 3.6 g. of diethyl 2-methylene-4-carbethoxypimelate were obtained from the residue.

In a similar way, there is employed morpholinodiphenyl phosphine or pyrrolidinyldioctyl phosphine as catalyst.

We claim:

1. A method for the preparation of dimers and trimers of acrylates having the formula:

CH =CHCOOR in 50 ml.

in which R is alkyl of 1 to 18 carbon atoms, comprising reacting said acrylates in the presence of a catalyst selected from the class consisting of:

and

in which R is selected from the class consisting of alkyl of 1 to 18 carbon atoms, phenyl and alkyl-substituted phenyl, in which the alkyl substituent contains a total of from 1 to 8 carbon atoms;

R" and R', individually, represent alkyl of 1 to 18 carbon atoms and collectively with the nitrogen atom to which they are attached form saturated cyclic amine radicals selected from the group consisting of piperidinyl morpholinyl and pyrrolidinyl, said R" and R' being joined to the nitrogen atom on a primary carbon atom.

2. The method according to claim 1, in which the catalyst (I) is used in an amount of at least 0.25 mole percent with respect to the acrylate reactant and the reaction is conducted in the range of about to 100 C.

3. The method according to claim 1, in which the catalyst (II) is used in an amount of at least 3 mole percent 6 with respect to the acrylate reactant and the reaction is conducted in the range of about 0 to 100 C.

4. The method according to claim 1, in which the catalyst (I) is used in an amount of at least 0.7 to 1.5 mole percent with respect to the acrylate reactant and the reaction is conducted in the range of about 25 to C.

5. The method according to claim 1, in which the catalyst (II) is used in an amount of at least 3 to 5 mole percent with respect to the acrylate reactant and the reaction is conducted in the range of about 25 to 85 C.

6. The method according to claim 2, wherein the catalyst employed is phenyldipiperidyl phosphine.

7. The method according to claim 2, wherein the catalyst employed is N,N,N',N-tetraethyl-P-phenylphosphonous diamide.

8. The method according to claim 2, wherein the catalyst employed is N,N,N',N-tetramethyl-P-phenylphosphonous diamide.

9. The method according to claim 3, wherein the catalyst employed is N,N-dibutyl-P,P-diphenylphosphinous amide.

10. The method according to claim 3, wherein the catalyst employed is N,N-dimethyl-P,P-ditolylphosphinous amide.

No references cited.

RICHARD K. JACKSON, Primary Examiner. T. L. GALLOWAY, Assistant Examiner. 

1. A METHOD FOR THE PREPARATION OF DIMERS AND TRIMERS OF ACRYLATES HAVING THE FORMULA: 